Revision session 1 Flashcards
Describe the structure of the retina
Central retina: macula.. The middle of the macula is the fovea: highly dense in photoreceptors including cone cells, important for colour vision.
The peripheral retina contains rod cells, which are essential for night vision as well as side vision
The retina has a neural component: this generates, amplifies and transports electrical signals
It has a retinal pigmented layer provides functional and metabolic support for the photoreceptors
Unilateral blindness caused by
Optic nerve lesion
Optic chiasm lesion causes
Bitemporal hemianopia
Lesion at the left optic tract
Right homonymous hemianopia
Differentials for a superior quadratinopia
Temporal lobe lesion
Bitemporal superior quadratinopia ddx?
Pressure from below: common pituitary tumours
Bitemporal inferior quadratinopia ddx?
Craniopharyngioma, meningioma, carotid aneurysm
Causes of glaucomatous defects?
Arcuate scrotoma
Causes of an enlarged blind spot?
Papilloedema or myopic periparliary atrophy
Central scrotoma
macular degeneration, optic neuritis, toxic ambylopia
Peripheral field constriction?
Glaucoma, retinitis pigmentosa, poisons, bilateral occipital lobe infarcts
Altitudinal defects?
Ischaemic optic neuropathy, occlusion of 1xt branch of retinal artery or vein
Defect crossing vertical/horizontal axes
retinal pathology – eg. detachment
Blood supply of macular fibres
Posterior cerebral artery
Occipital branch of MCA
hence macular sparing hemianopias
Describe the optic chiasm
Where nasal retinal fibres cross
